public class HashBunk2<K, V> {
    static class Node<K, V> {
        public K key;
        public V val;
        public Node<K, V> next;

        public Node(K key, V val) {
            this.key = key;
            this.val = val;
        }
    }

    public Node<K, V>[] array = (Node<K, V>[]) new Node[10];
    public int usedSize;

    public static final double LOAD_FACTOR = 0.75;

    public void put(K key, V val) {
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K, V> cur = array[index];
        while (cur != null) {
            if (cur.key.equals(key)) {
                cur.val = val;
                return;
            }
            cur = cur.next;
        }
        // 采用头插法
        Node node = new Node<>(key, val);
        node.next = array[index];
        array[index] = node;
        usedSize++;
        if (calculateLoadFactor() >= LOAD_FACTOR) {
            // 扩容
            resize();
        }
    }

    public V get(K key) {
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            if (cur.key.equals(key)){
                return cur.val;
            }
            cur = cur.next;
        }
        return null;
    }

    private void resize() {
        Node<K, V>[] newArray = (Node<K, V>[]) new Node[2 * array.length];
        for (int i = 0; i < array.length; i++) {
            Node cur = array[i];
            while (cur != null) {
                // 保留cur.next
                Node curNext = cur.next;
                int hash = cur.hashCode();
                int index = hash % newArray.length; // 找到了在新的数组当中的位置
                cur.next = newArray[index];
                newArray[index] = cur;
                cur = curNext;
            }
        }
        array = newArray;
    }


    // 计算负载因子
    private double calculateLoadFactor() {
        return usedSize * 1.0 / array.length;
    }


}
